Method and apparatus for disconnecting well pipe joints



July 8, 1958 F. l. ALEXANDER METHOD AND APPARATUS -FOR DISCONNECTING WELL PIPE JOINTS 41.5 )c4/vage IN V EN TOR.

BY /mfm United States Patent C) METHOD AND APPARATUS Fon' DISCON- NECTING WELL PIPE JolNrs Ford I. Alexander, Arcadia, Calif. Application september 6 1955', serial No. 532,636

z claims. (Clt. 16s-46) This invention relates to improved methodsvand apparatus for breaking a joint,-deep within a wel1between two stands of a stuck drill string or other well pipe.

When a rotary drilling stm'ng becomes stuck in a well, as a result of a caveein or similar condition, it is desirable to disconnect whichever joint of the pipe is just above the stuck location, and to then remove. theupper free portion ofthe string. from the well. The problem thus arises of breaking that particularv joint of the string while leaving. all of the other joints intaC., so that as much of the` pipe is recovered as possible.

The general, Object- Of the Present invention is te previde an improved method for this purpose which will very eieetively' break a `predetermined single joint-deep within a well, and yetwill do so in a manner avoiding any possibility of damage to that joint or to any other portion of the stringduring the loosening operation. `At the same time, the present method is adapted for'very easy and reliable control from the surface of the earth.

Further contemplated is a type of apparatus which can function, on a single run within a well, to first locate the stuck pointV of a drill pipe, and then loosen the joint directly above that point. Heretofore, these two operations have required' two. separate runs into the well with two diierent units, since the type of loosening operation normally utilized has employed an explosive, whose liring would damage the very sensitive type of instruments utilized as stuck point indicators.

In order to achieve the 'above results, I employ a method which involves the application of both force and heat to the joint, so that the force and heat togethercause the desired breaking of the joint. More particul2 1rlyll apply force. to the stringy tending toL break the joillt, and in conjunction with5 the-force, I apply heatlocall'y tothe joint. in an amount raising the joint to, a veryy highftemfperature sueienttoy initiate unscrewing of the joint under'the applied` force. The, force may be a torque tending. to unscrew the joint, or a lifting force relieving the joint of the, weight of Athe string. Preferably, both a torque and a. lifting force are utilized. If diliicultyV is encountered, the lifting force. may be alternately applied and` relieved, in a manner tending. to vertically reciprocate the string while it is heated.

The heat may be applied by a relatively small heater lowered into theA well, typically either an electric heater ora burner unit carrying a suitable combustible material. The heater may include means for holding -the heater bodyA laterally against one sidev of the well pipe,-a s by provision ofv magnetic means on the heater attractable to the pipe. When lowered into a pipe, the heater may. be connectedgto ar stuck point indicator for locating the highest point at which` the pipe is stuck, and also to. a joint'linder for locating the nearest joint in the pipe after the stuck point is found.

The above and other features and objects of the present invention will be better understood from the following i 2,842,207 Patented July 8, 1958 2 detailed description of the typical embodiment represented in the accompanying drawing in which:

Fig. lis a partially schematic representation of a well containing a stuck. drill string, together with the apparatus which is utilized for breaking one of the joints of the string directly above the stuck point;

Fig. 2 is an enlarged fragmentary vertical section through a portion of the Fig. 1 apparatus, and

Fig. 3 is a fragmentary sectional view similar to Fig. 2, but showing a variational type of heater for raising the temperature of the joint which is to be broken.

Referring first to Fig. 1, I have shown at 10 a well bore, containing a rotary drilling. string 12 or other pipe string which hasbecorne stuck in the well. The lower portion of the drill string 12 may be considered as being stuck up to Aa point 13, typically by caving in of the lower portion of the well in a manner tightly packing the earth about the drill string, Above the point 13, the string 12 is free, and it is therefore desired to break the nearest threaded joint 14 above point 13, so that the portion of the string iabove joint 14 may be recovered from the well. l

As seen best in Fig. 2, each of the joints 14 of the drill string 12 includes the usual threaded pin and box sections 15 'and 16 which are connected together by right hand rotation of the pin section, and which are then eiective to transmit rotary motion from thefpin section to the box section, so that rotation of the upper end of the drill string in a iight hand direction turns the entire string during a drilling operation. The threads 17 interconnecting sections 15 and 16 are normally of a tapered configuration, as shown, and made up sutliciently tightly to require a considerable unwinding torque in Y order to break the joint.

The movements ofthe drill string are controlled by the usual equipment 18l at the surface of the earth, in cluding a power driven rotary table 19adapted to receive slips 20 for suspending the weight-of string`f'12. The rig 18 includes also a derrick 21, havinga traveling block 22 from which string 12 may be, supported by a suspension element 23, block 22 being movable upwardly by winding of its cable 24 on theV usual power driven elevating drum 25.

For conditioning a particular joint 1410 be broken by forces exerted by the rotary .table and traveling block, I lower into the well on a suspending cable 26 a heater 27, which acts to internally heat the drill string at the desired lowermost free joint 14, to a temperature such that vertical and rotary forces exerted against the upper end of the pipe by the rotary table and traveling block will be effective to break the desired joint, while leaving the other joints of the string intact. This heater 27 may include a vertically elongated tubular preferably metal and uid tight outer housing 28, containing a suitably insulated electrical heater element or coil 29, adapted tobe energized by current from a suitable electrical power source 30 at the surface of the earth. One side of the power source 30 may be connected to heater element 29 through a ground connection 31, while the other side of power source 30 may be connected to the heater element through a switch 32 anda lead 33 extending downwardly within the well. The heater 27 is preferably of a length somewhat greater than the length of the threaded joint which. is to be broken. Also, it is desirable to provide some means for holding heater 27 laterally against and in heat transferring engagement with one sideof the inner wall of the joint (see Fig. 2). Such positioning of the heater may be eiected by permanently magnetizing .the outer magnetic metal housing 28 of heater 27, typically by making its upper end a north pole and itsylowef end a southy pole, so that the magnetized housing automatically clings to one side of the steel drill pipe. The weight of the heater must of course be sutlicient to cause lowering of the heater in spite of the described magnetic attraction, when such lowering is permitted by the suspending cable 26. 7

Cable 26 also preferably suspends, desirably at a location above heater 27, a conventional free point indicator or stuck point indicator 34, which electrically controls an associated indicating unit 135 at the surface of the earth, in a' manner such that the indicator locates the uppermost point 13 at which string 12 is stuck. This free point indicator may be of any of the well known types now in use, and need not be described in detail for present purposes. To describe the free point indicator 34 very briey, this device includes two tubular vertically extending elements or sections 35 which interfit telescopically at 36 in almanner allowing relative vertical telescopic movement of the two sections. A set of upper bowed springs 37 carried by the upper section 35 of device 34 acts to frictionally hold that section in a particular set position within drill string 12, while a second and lower set of springs 38 acts to correspondingly frictionally hold the lower section 35 in a desired set position. When unit 34 is lowered into the drill string to a particular location, and traveling block 22 is then actuated to exert a vertical force against the string, the resulting slight relative movement of the two sections 3S of unit 34 acts through a strain gauge or other responsive member contained within the device to produce an electrical response which is indicated to an operator at the surface of the earth on the indicating unit 135. If this same type of operation is performed with free point indicator 34 positioned in string 12 at a location beneath the stuck point or free point 13, the engaged portion of the string of course will not be elongated or extended even slightly when traveling block 22 is actuated to exert an upward force on the string, so that the indicating unit 135 will apprise an operator of thevfact that the unit 34 is within a stuck portion of the'pipe. By thus taking aser'ies of readings from stuck point indicator 34, it is possible to very precisely locate the uppermostpoint 13 at which the drill pipe is stuck.

After the point 13 has thus been determined, it is desirable to elevate heater 27 upwardly to its Fig. l position within the next upper joint 14, in order that that joint may be broken. To locate the joint 14 for such positioning of heater 27, I suspend on cable 26, in addition to heater 27 and free point indicator 34 (and preferably vertically therebetween and substantially directly adjacent heater 27) a conventional instrument of the type referred to as an electrical joint finder, designated 39 in the drawing. As in the case of instrument 34, it is unnecessary for present purposes to describe specically the construction of joint finder 39, other than to say that it includes a body or housing 40 movably carrying a laterally projecting and typically spring pressed, finger or element 41, which is deflected relative to body 40 by engagement with the reduced dimension portion 42 of the drill string at each joint 14, and which electrically controls an indicator 43 at the surface of the earth to tell when joint finder 39 is positioned within one of the joints 14.

As an example of one of the various types of conventional stuck point indicators which have been utilized commercially in the past, reference is made to U. S. Patents 2,530,308 and 2,530,309. Similarly, as an example of the type of device which could be utilized as the joint finder" in the present apparatus, reference is made to U. S. Patent 2,322,343.

In performing a joint breaking operation in accordance with the present method, a first step may be to lower the instruments 27, 39 and 34 into the stuck drill pipe 12. The drill pipe elevating mechanism 22-25 may then be actuated, by driving drum 25, to exert an upward force on the upper end of drill string 12, this upward force or movement preferably being sutlicient to lift substantially all of the weight of the drill string oi of the joint 14. Slips 20 may then be inserted into the rotary table, so that the drill pipe is suspended from the rotary table in the described condition in which the weight of the pipe is relieved from joint 14. Rotary table 19 is then driven in a left hand direction with a force to apply a very substantial unscrewing torque to the upper pin section 15 of the joint 14 which is to be unscrewed. This torque is suficiently great to perform the desired function of assisting in breaking the joint 14, .while at the same time being insufficient to twist ot or otherwise damage the pipe.

Heater 27 is properly located within the desired joint 14 by first utilizing free point indicator 35 to determine the exact location of the uppermost stuck point 13, following which cable 26 is pulled upwardly to a point at which indicating unit 43 responsive at joint finder 39 indicates that instrument 39 is located directly within the nearest joint 14 above point 13. After this position has beenlocated, cable 26 is raised through a predetermined measured distance corresponding to the effective vertical spacingbetween unit 39 and heater 27, which raising of cable 26 is just sufcient to very accurately locate heater 27 in its Figs. l and 2 position Within joint 14,

With heater 27 positioned as shown in Fig. 2 within joint 14, and with the Weight of string 12 suspended and an unscrewing torque applied by rotary table 19 as previously discussed, switch 32 at the surface of the earth may be closed to energize heater 27 and thus raise the temperature of the pin and box ends interconnected at joint 14. Since the outer metal casing of heater 27, which is directly heated by element 29, is in direct heat transferring engagement with the metal of the two joint sections at the joint location, heater 27 is capable of very effectively and directly heating the joint sections to a rather high temperature. This causes expansion of the two threadedly interconnected sections, which expansion causes sufficient relative movement of the sections to somewhat loosen the heated threaded joint so that the torque and suspending forces exerted against the drill string will unscrew the heated joint (without unscrewing the unheated joints thereabove). If the joint does not break when the temperature is thus raised by heater 27, slips 20 may be removed from the rotary table 19, and drum 25 may be alternately driven several times in opposite rotary directions to alternately exert an upward force against the drill string and then allow the weight of the string to again rest on the'joint 14. Preferably, during such repeated suspension and release of the drill string, an unscrewing torque is exerted against the upper section of the drill pipe, as by a suitable power tong or other unit typically represented at 44, acting to apply a torque of the same value previously described in connection with rotary table 19. Thus, the combined heating, torque application, and vertical working of the drill stringwill serve to break even the most tightly made joint 14. After the threaded connection is broken, the instruments 27, 39 and 34 may be withdrawn upwardly from the well, and rotary table 19 may be driven to oomplete the unscrewing of the upper portion of the pipe from the lower stuck portion at joint 14, following which the upper portion may be removed upwardly from the well, leaving the lower stuck portion in the well. Subsequent operations may of course be performed to free a portion or all of the stuck pipe, so that it too may be removed from the well.

Fig. 3 represents fragmentarily a variational form of the invention, which is identical with that of Figs. 1 and 2 except as to the type of heater 27a which is employed. This heater 27a is suspended by a cable 26a beneath units ofthe type previously described at 34 and 39. Heater 27a comprises an outer vertically extending tubular housing 28a, filled with a mass of highly combustible material, which is adapted when ignited by an electrically energized fuse 45 to produce a very high temperature Within the threaded pipe joint 14a. The hot gases produced by ignition of charge 29a may be directed outwardly through apertures 145 in the side of housing 28a against the threaded portion of the joint. Housing 28a is preferably formed of suiiciently rigid metal or other material to effectively withstand the pressure and high temperatures encountered upon burning of charge 29a. The charge 29a is formed of a material which is adapted to burn effectively when completely submerged in water or other well liquid, and may initially be completely sealed from the well liquid by lluid tight plugs 47 received in apertures 46 and adapted to be easily ejected from those apertures by the pressure developed during burning of charge 29a.

Whether the heater employed is of the type shown at 27, or that shown at 27a, or some other type of heater, it must be capable of raising the temperature of the threaded joint sections under normal well conditions to a rather high temperature, preferably to a temperature at least about 250 F. higher than the temperature of the joint being heated and the adjacent formation prior to heating. However, the temperature rise should not be great enough to destroy the temper or substantially affect the hardness of the metal of the string sections or their joint ends, and for this purpose the heater should not elevate the joint or string temperature higher than about 950 F. The heat from heater 27 or 27a is desirably applied over a somewhat extended period of time, rather than merely instantaneously, the heat preferably being applied over a period of at least about one minute, and desirably between one and ten minutes. If the joint is still stuck after being heated for a substantial period of time, say ten minutes, the heater may then be alternately turned olf and on for a few minutes at a time, to cause the joint to alternately expand and contract, and thus increase the possibility of breaking the joint.

Where a heater of the type shown at 27a is employed, the burning charge 29a may be formed of any suitable slow burning material or mixture, such as black powder mixed with sawdust to slow its burning rate, and suitably compounded to burn when submerged in well uid.

I claim:

1. The method of breaking a threaded joint deep within a well between sections of a string of pipe stuck in the well, that comprises applying force to the string above said joint tending to break the joint, locally heating said joint from the inside thereof, and loosening the joint by the heat induced expansion thereof to an extent such that said force becomes effective to unscrew said joint, said force including a lifting force alternately applied and relieved to tend to vertically reciprocate the string.

2. The method of breaking a threaded joint deep within a well between sections of a string of pipe stuck in the well, that comprises alternately applying to the string and relieving a lifting force to tend to vertically reciprocate the string, applying a torque to the upper portion of the string tending to unscrew the joint, locally heating said joint from the inside thereof, and loosening the joint by the heat induced expansion thereof to an extent such that said alternately applied and relieved lifting force and said torque become effective to unscrew said joint, said heating being continued for at least about one minute, and acting to raise the temperature of saidjoint at least about 250 degrees F. above the ambient temperature at said joint.

References Cited in the le of this patent UNITED STATES PATENTS 

